JPH04215751A - Coxa intramedullary screw - Google Patents

Abstract

PURPOSE: To enhance the slidable compression of a selected broken born part with the use of an intramedullary rod and a sleeve inserted toward the femur neck piercing through the proximal part of the intramedullary rod by making the slidability obtained only by a compressive hip joint screw assembly and the reposition of the broken born part based thereupon strict. CONSTITUTION: An intrameduallary screw includes an intramedullary rod 20, a rack screw 60 and a sleeve 40 slidably accommodating therein with the lack screw. The sleeve 40 is accommodated in a passage 28 formed in the rod 20 having an axis oblique to the longitudinal axis of the rod 20 so that the axis of the sleeve 40 is directed toward the femur neck. The intramedullary screw according to the present invention enables slidable compression of a broken born part, in particular, slidable compression of an intertrochanteric fracture and a fracture of the femur neck.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to an instrument for treating femoral fractures.

0002

BACKGROUND OF THE INVENTION There are various instruments used to treat femur fractures. Intertrochanteric fractures of the femur, as well as fractures of the femoral neck or head, have been successfully treated using a variety of compression hip screw assemblies. The compression hip screw assembly generally includes a compression plate with a barrel member, a lug screw, and a compression screw. The compression plate is fixed to the outside of the femur, and the barrel member is inserted into a hole previously drilled in the direction of the femur. The lag screw has a threaded end and a smooth portion and is inserted through the barrel member. The lag screw thus extends through the fracture and into the femoral head. A compression screw connects the lag screw to the compression plate. By adjusting the tension of the compression screw, the compression (reduction) of the fracture is adjusted. To allow adjustment of the compression screw, the smooth portion of the lug screw must be slidable within the barrel member. Because the barrel member is long relative to its diameter, the force required for sliding, ie, the force required to maintain reduction of the fracture, is minimal. However, compression hip screw assemblies require long incisions in the tissue near the fracture site;
Also, compression plates located on the outside of the bone may displace under force, thus creating long moment arms and subjecting the implant to very high tensions.

Compression hip joint screw assembly is disclosed in US Pat. No. 443
No. 2358, No. 3374786, No. 2702543, No. 4530355, No. 3094120 and No. 38
No. 42825. U.S. Patent No. 30941
No. 20 and No. 3,842,825 use multiple screws to prevent the lug screw from rotating relative to the compression plate or barrel member. US Pat. No. 3,103,926 discloses a surgical bone pin that functions like a lag screw and a compression screw, but without a compression plate.

Subtrochanteric and femoral shaft fractures are treated using an intramedullary rod that is inserted into the intramedullary canal of the femur to immobilize the portion of the femur involved in the fracture. Square cross nail (ang
A single set screw (cross nail) is inserted through the femur and the proximal end of the intramedullary rod. In some variations, one or two other screws may be inserted through the femoral shaft and the distal end of the intramedullary rod. Standard intramedullary rods have been used with good results in the treatment of fractures of the lower femoral shaft.

[0005] Grosse-Kemp (Gr.
The Osse-Kempf nail is said to be one of the oldest intramedullary nails introduced in the United States. The Grosse-Kemp nail has a threaded hole in the intramedullary rod that receives a mating screw. A fully threaded screw cannot slide through a threaded hole to enable the type of compression found in the compression hip screw assemblies described above. Furthermore, the axes of the screw holes coincide with the straight line between the greater and lesser trochanters, but do not coincide in the direction of the femoral neck.

US Pat. No. 3,433,220 discloses an intramedullary rod and cross nail assembly useful for treating fractures of the upper third of the femur or the lower trochanter. The Zickel nail is a solid intramedullary nail with one proximal trilobal flange cross nail inserted toward the femoral head.

Such rigid three-lobed flange cross nails are not suitable for the treatment of femoral neck fractures because the cross nail must be fixed in position by set screws to prevent it from slipping out. Adequate compression cannot be obtained. As previously mentioned, sliding compression screws have been shown to be the most effective treatment for femoral neck fractures.

US Pat. No. 4,827,917 discloses an intramedullary rod and an intramedullary rod designed to be inserted through the proximal portion of the rod toward the femoral neck to enable sliding compression of a selected fracture site. A femoral fracture treatment device is disclosed that includes a screw.

[0009]

SUMMARY OF THE INVENTION The present invention provides the sliding properties and fracture reduction provided by conventional compression hip joint screw assemblies that are more precise than those provided by conventional compression hip joint screw assemblies. The aim is to further improve the advantages achieved by the device disclosed in the patent.

The present invention provides a femoral fracture treatment device having a lag screw, a sleeve, and an intramedullary rod. The present invention thus provides: a lag screw having an elongated body member and means formed at one end of the body and configured to engage a large medullary head in use; a hollow sleeve slidably receiving said lag screw; and an intramedullary rod having a proximal head portion and a stem distal to the head portion, the intramedullary rod being configured for insertion into an intramedullary canal of a femur in use, wherein the head portion is connected to the sleeve. in order to accept
at least one passageway passing through the head, said passageway being positioned obliquely to the longitudinal axis of said rod such that when said rod is located within an intramedullary canal of a femur, said passageway axis is To provide a treatment instrument for femoral fractures, which is tilted toward the femoral head.

The lag screw has an elongate body member and an engagement means formed at one end thereof and configured to engage the femoral head. The intramedullary rod has a longitudinal axis, a proximal head portion and a stem portion distal thereto. In use, the intramedullary rod is inserted into the intramedullary canal of the femur. The head of the intramedullary rod is
It has at least one passageway extending therethrough for receiving the sleeve. A hollow sleeve slidably receives a lag screw. The passageway of the intramedullary rod is such that the axis of the passageway and the sleeve and lag screw inserted through the passageway are oriented or inclined toward the femoral head when the rod is properly positioned within the intramedullary canal of the femur. Located diagonally in a direction at an angle to the longitudinal axis of the rod.

Preferably, a means such as a compression screw receivable within the lag screw is provided for cooperation with the lag screw and sleeve to apply a sliding compressive force to a selected fracture of the femur. The sleeve includes an engagement surface formed within the sleeve and configured to cooperate with a complementary engagement surface formed on the body member of the lag screw to prevent rotation of the lag screw within the sleeve. may be provided.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The hip joint intramedullary screw of the present invention will be described and explained in more detail below with reference to the attached drawings.

FIG. 1 is a side sectional view of the hip joint intramedullary screw of the present invention.

FIG. 2 is a side cross-sectional view of the intramedullary rod of FIG.

FIG. 3 is a side sectional view of the sleeve of FIG. 1.

FIG. 4 is a sectional view taken along the line IV--IV in FIG.

FIG. 5 is a side cross-sectional view of the lag screw of FIG. 1.

FIG. 6 is a side view of the compression screw of FIG. 1.

1-6 illustrate preferred embodiments of the components of the hip intramedullary screw 10 of the present invention. The hip joint intramedullary screw 10 generally includes an intramedullary rod 20, a sleeve 40, and a lag screw 30. Set screw 80 and compression screw 90
is also provided in a preferred embodiment of the invention. Hip intramedullary screw 10 may be manufactured from any suitable high strength biocompatible material. Stainless steel, titanium or chromium-cobalt are preferred.

FIG. 2 will be explained. Intramedullary rod 20 includes a proximal head 22 , a stem 24 distal to head 22 and an optional longitudinal bore 26 . Head portion 22 includes a passageway 28 extending through rod 20 . The axis of passageway 28 is angled relative to the longitudinal axis of rod 20 and is oriented toward the femoral head in use. The above angle is preferably about 30° to 50°. Preferably, the holes 26 extend through the entire length of the rod 20, but may be provided along only a portion of the length of the rod 20.

[0022] The rod 20 has a counterbore with an internal thread and an elongated hole 34 at the opening.
30 to receive a threaded set screw 80 and a prong of an instrument for aligning the rod 20 into the femur. In one embodiment of the rod 20, the through hole 32 (2
a bolt, screw, nail or some other suitable known fixing means is passed through the hole to place the stem of the rod 20 in the appropriate position within the intramedullary canal of the femur. 24 is fixed. A through hole 32 passes through the hole 20 transversely, preferably at right angles, to the longitudinal axis of the rod 20. A plurality of through holes 3 are provided along the length of the stem 24.
2 can be provided and fixed at one or more desired positions. Further, in other embodiments of the rod 20, the through hole 32 is not provided.

An additional hole 36 is provided in the head portion 22 of the rod 20 through which an additional pin (not shown) can pass to provide additional fixation. The additional through hole 36 is
If provided, it is smaller than the passage 28. Additional holes are
When the pin is located above the passageway 28, the set screw 80
It must be eccentric so that it can be avoided.

As shown in FIGS. 1 and 3, sleeve 40 includes a central hole 42. As shown in FIGS. Sleeve 40 is received in passage 28 of rod 20 and is longer than passage 28. sleeve 4
The zero length is greater than its diameter in relative proportions typical for compression plate barrel members used in prior art instruments. Preferably, the through hole 42 is provided with a key. In FIG. 4, the through hole 42 includes opposing flat surfaces 44. As shown in FIG. The outer surface of the sleeve 40 is preferably provided with a groove 50 for cooperating with a set screw 80.

Lag screw 60 includes an elongate body member 62 and a threaded end 64. The body member 62 is preferably keyed at its distal end and includes an opposing flat surface 66 that complementarily cooperates with the flat surface 44 of the sleeve 40. As shown in FIG. 1, lag screw 60 is slidably received within sleeve 40. As shown in FIG. Surfaces 44 and 66 cooperate to prevent lag screw 40 from rotating within sleeve 40 while lag screw 60
0 can be slid in the axial direction. The outer diameter of the threads of threaded end 64 is the same as that of body member 62.
It is preferable that the diameter is larger than the diameter of . Preferably, the outer diameter of the sleeve 40 is approximately equal to the outer thread diameter of the lag screw 60. The above dimensions of the threaded end 64 allow for a larger purchase of the femoral head, which is particularly advantageous for treating elderly patients or patients with degenerative bone disorders.

The lag screw 60 is also a threaded compression screw 90.
It is provided with a female threaded hole 68 for receiving.

Compression screw 90 cooperates with lag screw 60 and sleeve 40 to apply a compressive sliding force to the fracture.

Compression screw 90 has a threaded shank 92 and a flat-bottomed head 94 having a diameter greater than the diameter of bore 42 in sleeve 60. Thus, when the compression screw 90 is tightened into the lag screw 60, the head 94 compresses the distal end of the sleeve to provide compression to the bone that is conventionally found only in compression hip screw assemblies having an external compression plate.

The set screw 80 has a smooth shank 82.
, a flat bottom 84 and a threaded head 86 are preferred. The flat bottom 84 is the preferred means of engagement when engaging the groove 50 of the sleeve 40 and provides excellent mechanical interlocking of the parts. Threads in head portion 86 engage threads in counterbore 30 of rod 20.

Another embodiment of the hip joint intramedullary screw 10 of the present invention includes rods 20 of different lengths. The rod 20 may have an internal bore or partial bore as shown, or it may be solid in cross-section except for the passageway 28 and either the bores 32 or 36.

The hip intramedullary screw 10 of the present invention can be inserted into a patient in any suitable known manner. Generally, the intramedullary canal of the femur is first reamed with appropriate instruments.
) to create a void into which the rod 20 is inserted. The void is reamed to approximately 1 mm to allow sufficient space for blood to flow after rod 20 is inserted. A guide pin or wire is optionally inserted into the reamed intramedullary canal of the femur. Rod 20 is then introduced into the desired location. When rod 20 is provided with hole 26, rod 20 is introduced onto the guide wire. At this time, the position must be confirmed using the normal image sensitization method.

[0032] Once rod 20 is properly oriented, lag screw 60 is aligned with passageway 28 with suitable conventional instruments. The area is properly reamed and the lag screw 60
is inserted into passageway 28 by means of a guide wire and appropriate conventional instruments. Threaded end 64 of lag screw 60 engages the femoral head. The smooth elongated body member 62 slides easily within the passageway 28.

The sleeve 40 is attached to the main body member 6 of the lag screw.
2 and inserted into the passageway 28 of the rod 20. sleeve 4
0 surface 44 is aligned with surface 66 of body member 62. The set screw 80 is then inserted through the top of the rod 20 so that the edge of the bottom 84 fits into the groove of the sleeve 40.
0 and is tightened until it engages and secures the sleeve 40 within the passageway 28.

Compression screw 90 is then optionally inserted into hole 68 of lag screw 60 and tightened with a suitable instrument until the flat bottom of head 94 presses against the distal end of sleeve 40. In cooperation with lag screw 60 and sleeve 40, compression screw 90 is tightened to apply the desired compression force to the fracture. The smooth elongated body member 62 of the lag screw 60 slides freely within the bore 42 of the sleeve 40.

If desired, to insert the fixation means through the hole 32 in the stem 24 of the rod 20, the hole is reamed with a suitable instrument to create a passage through the bone. Similarly, an appropriately sized hole may be reamed if desired to allow insertion of an anchor pin into the additional hole 36 in the head 22 of the rod 20.

The hip intramedullary screw 10 of the present invention has advantages over conventional compression screw assemblies. This is because it requires a very small incision for insertion, which causes less trauma to the fracture area.

[0037] Attach the lag screw 60 and sleeve 4 to the intramedullary rod.
Penetrating 0 significantly reduces the loaded moment arm and therefore reduces the load that the implant must carry. Reducing the load on the implant reduces the chance of implant failure. This design of the hip intramedullary screw 10 facilitates fracture compression compared to previously available femoral fracture instruments by increasing the area over which the lag screw 60 slides. Body member 62 of lag screw 60
The length of the sleeve 40 over which it slides is greater than the corresponding sliding area provided in, for example, the femoral fracture instrument described in previously discussed US Pat. No. 4,827,917. Compression screw 90 connects sleeve 40 and lag screw 60
This jointly eliminates the high tensile forces on the implant of the compression hip screw assembly to provide the advantages of sliding compression available in compression hip screw assemblies and the advantages of fixation of the intramedullary passageway.

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view of the hip intramedullary screw of the present invention.

FIG. 2 is a side cross-sectional view of the intramedullary rod of FIG. 1;

FIG. 3 is a side cross-sectional view of the sleeve of FIG. 1;

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3;

FIG. 5 is a side cross-sectional view of the lag screw of FIG. 1;

FIG. 6 is a side view of the compression screw of FIG. 1;

[Explanation of symbols]

20 Intramedullary rod 22 Proximal head part 24 Stem 28 Passage 30 Countersink hole 40 Sleeve 50 groove 60 Lag screw 80 Set screw 90 Compression screw

Claims (5)

[Claims] 1. A lag screw having an elongate body member and means formed at one end of the body and configured to engage a large medullary head in use; a hollow sleeve slidably receiving the lag screw; and an intramedullary rod having a proximal head portion and a stem distal to the head portion, the intramedullary rod being configured for insertion into an intramedullary canal of a femur in use, wherein the head portion is connected to the sleeve. at least one passageway through the head portion for receiving the rod, the passageway being positioned obliquely to the longitudinal axis of the rod, when the rod is located within the intramedullary canal of the femur; A device for treating femoral fractures, wherein the axis of the passageway is angled toward the femoral head. 2. The device of claim 1, further comprising means for cooperating with said lag screw and said sleeve to apply a sliding compressive force to a selected fracture of the femur. 3. Further comprising a first engagement surface formed on an inner surface of the sleeve and a complementary engagement surface formed on an outer side of the main body member of the lag screw, the first engagement surface and 3. The device of claim 1 or 2, wherein complementary engagement surfaces are configured to cooperate to prevent rotation of the lag screw when the lag screw is inserted into the sleeve. 4. The rod has a longitudinal hole through which at least a portion thereof extends.
The equipment described in. 5. An engagement means formed on the outside of the sleeve, and a set screw inserted through the hole in the rod and configured to mesh and engage with the engagement means on the sleeve. A device according to claim 1.